Alloy



Patented Feb. 7, 1939 Howard W. Russell, Columbus,

Elgin National Watch corporation of Illinois Ohio, assignor to Company, Elgin, a

No Drawing. Application April 20, 1938,

Serial No. 203,198

Claims. (01. 75-128) This inventiompertains to a ferrous-nickel alloy. While predominantly ferrous-nickel, this alloy also has manganese, chromium, tungsten, carbon, and silicon'as essential ingredients.

A novel and useful alloy of these elements is described in the following parts of the specification.

The present alloy has been developed after a careful study and extensive tests, the object of form and non-anomalous thermal expansion.

which was to produce a watch hairspring having certain desired characteristics.

Compensating hairsprings are used with balance wheels having continuous mono-metallic rims, in lieu of the more delicate and expensive balances of the divided bi-metallic rim type. It is the function of a compensating spring to increase in strength with increase of temperature in such proportions as to compensate for a simultaneous increase in the moment of inertia of the balance wheel; and to decrease similarly in strength with decreases in temperature.

. An ideal spring of this nature must have a uni- Its thermo-elastic coeflicient should be as low as possible, and fixed and definite over a temperature range from ,minus 4 degrees F. to 95 degrees F.

Such a compensating spring should be nonmagnetic and non-corrosive.

It must have suitable mechanical properties which include hardness with high tensile and torsional strength, so that a small size is sufiicient, a high elastic limit, capability of annealing to a soft and workable condition, with fixing of properties and shape by simple subsequent 4 treatment.

The properties of the completed spring should not change with time, whether the spring is in stock or in use. There should be no aging factor with respect to strength, creep, or hardness.

There should be a considerable tolerance of V proportions employed, so that the desired properties can be reproduced easily without minute control of proportioning and mixing. In the heat treatments there should be a corresponding tolerance, and these heat treatments should be simple and easily supervised.

Springs made from the alloy of the present invention meet all of the prescribed conditions in a high degree. Therefore, it will be apparent that corresponding demands for an alloy for other purposes have been satisfied.

- The general compositionof the alloy of this invention expressed as percentages by weight is:

vPercent Nickel 32.0 to 37.5 Manganese 5.00to 6.00' Chromium 4.00 to 8.00 Tungsten 1.95 to 2.20 5 Carbon- 0.60 to 0.75 Silicon 0.10 to 0.75

Iron and usual impurities (balance) 46.6 to 51.3

The predominant characteristics of the alloy of this invention are taken fro the substantially fixed ratio of the iron and nic e1 combination to the remaining elements. As shown in the statement of general composition, iron and nickel constitute not less than 80 or 85 per cent of the composition. By balancing of the other ingredients within the limits noted, the desired minor, but necessarily integrated, characteristics will be obtained.

The utilization of relatively high quantities of manganese is a feature of the invention. Hitherto manganese has been employed normally as a deoxidizer, in which event it substantially disappears from the final alloy as worked.

In general, manganese, tungsten, and carbon 05 can be profitably added in order to raise the elas- .tic limit of the present ferrous-nickel alloy.

Chromium and tungsten in the amounts specifled increase the stability of this alloy. The former also improves the corrosion-resisting proper- 3O ties and contributes to the hardness. Tungsten imparts also a desired toughness.

In the amounts defined, carbon serves to increase the yield point markedly and augmentsthe hardness produced by the other elements.

Silicon, within the percentages named is not harmful; it performs the very useful function of rendering the alloy forgeable.

The following is a preferred composition:

Percent 40 Nickel 34.8 to 35.5 Manganese s 5.45 to 6.00 Chrom m 5.00 to 5.25 Tungsten 1.95 to 2.20 Carbon 0.60 to 0.75 Silicon 0.45 to 0.75

Iron and usual impurities (balance) 49.5 to 50.2

As is customary, the ingredients of this alloy are melted together in any suitable furnace and then cast into an ingot of the required size. After appropriate annealing the ingot may be reduced to rods of small diameter by swaging and drawing.

The heat and mechanical treatments which have been found to give the best results for the alloys included'in the foregoing formula comprised the following steps:

A. Heating the hot rolled sections, which may be one-quarter inch rods W in the range from 1700 to 1800 degrees F. for substantially two hours.

13. Then cooling slowly.

C. Next cold drawing the rods to one-hundredth-inch (0.01") wire with as many annealing treatments during the drawing reduction as may be required.

D. Finally annealing the wire for two minutes in the range from 1800 to 1900 degrees F., preferably in a non-oxidizing atmosphere, and again cooling slowly.

After this last anneal the wire is ready to be drawn down to a hairspring size. Since a large share of the spring properties depend on the effect of cold work on the alloy, no further heat treatment is applied thereto, except the moderate one employed in setting the completed hairsprings.

After the recited heat and mechanical treatments, certain properties have been observed in specimens of articles so treated:

The thermo-elastic coefficient was substantially stable over a normal range of atmospheric temperatures, from -17 to +65 degrees C. to 150 degrees F.) For different alloys within the com position ranges set forth, the thermo-elastic coefficients were found to lie in the range from +1x10- to --1x10 per degrees centigrade.

The alloy of this invention is weakly magnetic when placed in a magnetic field. However, it

loses its magnetism immediately upon removal from the influence of such a field.

With further reference to the low thermoelastic coefficient of this alloy, it is noted that this characteristic is due to its peculiar magnetic properties. Evidences of peculiarity are found in the following test results.

At a temperature of about 290 degrees F., this alloy loses its magnetism entirely. ":In steel a like result is not obtainable appreciably below 1415 degrees F.

Whereas, this alloy below 290 degrees F. will lose its magnetism when removed from the magnetizing field, the steel ordinarily used for hairsprings will retain enough magnetism under like treatment seriously to impair its function as a hairspring.

A very high resistance to corrosion by indus-' trial atmospheres has been shown by the alloy of this invention. Immersion of the alloy in a fifteen per cent (15%) solution of either hydrochloric or sulphuric acid haspractically no effect.

The tensile strength of this alloy in the cold worked condition ranges from 175,000 to 195,000 pounds per square inch, depending on the amount of cold working it has received. Its yield point is very close to its tensile strength.

Because of the difficulty in obtaining reliable data on the tensile strength of the alloy in hairspring size, the figures of the preceding paragraph were obtained on wires ninety-one one thousandths of an inch (0.091) in diameter. How ever, it can be stated with certainty that the strength in hairspring size will not be lower than the range indicated above.

Other tests show that this alloy is not sensitive to elastic after effects". The elastic after effect manifests itself in the following manner. when a stress considerably below the yield point is imposed upon a test specimen of material, it will elongate a normal amount. If the load provclucingthisstressismaintainedtorsional):-

riod, e. g., several days. a slight additional elongation will be observed. Moreover, when the load is finally removed, the material will not return to its original dimensions immediately, but will require an appreciable time varying from a few hours to several months. This effect is much smaller for the alloy than it is for heat treated steel of the analysis ordinarily used for hairsprings.

I claim:

1. As an article of manufacture, a temperature compensating spring consisting of nickel substantially 34.8 to 35.5 percent, chromium 5.00 to 5.25 percent, manganese 5.45 to 6.00 percent, tungsten 1.95 to 2.20 percent, carbon 0.60 to 0.75 percent, silicon 0.45 to 0.75 percent, and the balance iron, the proportion 'of iron and nickel combined being not less than 85 percent, and the proportion of iron, nickel, chromium and manganese being not less than 95 percent, said spring having substantial stable elastic properties over a temperature range from 0 to 150 degrees F.

2. An alloy consisting of nickel substantially 35 percent, chromium substantially 5 percent, manganese substantially 5.5 percent, tungsten substantially 2 percent, silicon substantially 0.5 percent, carbon from 0.6 to 0.75 percent, and the balance iron with usual impurities, said alloy having substantially stable elastic properties over a temperature range from 0 to 150 degrees F., high tensile strength, very weak magnetic properties, and a high resistance to corrosion.

3. A hairspring made of an alloy comprised of 32 to 37.5 parts of nickel, 4 to 8 parts of chromium, 5 to 6 parts of manganese, 1.95 to 2.20 parts of tungsten, less than 0.75 parts of carbon and having 0.10 to 0.75 parts of silicon, and the remainder being iron with usual impurities; said hairspring being characterized by having the properties produced by heat treatment of such an alloy by maintaining the same at a temperature of substantially 1700 to 1800 degrees F. for substantially two hours, followed by a slow cooling and a further treatment at a temperature of substantially 1800 to 1900 degrees F. for substantially two minutes, and then followed by a further slow cooling, whereby the hairspring has the property of remaining substantially stable in respect of its elasticity over the normal range of operating temperatures.

4. A spring made of an allow comprised of 32 to 37.5 parts of nickel, 4 to 8 parts of chromium, 5 to 6 parts of manganese, 1.95 to 2.20 parts of tungsten, less than 0.75 parts of carbon, 0.10 to 0.75 parts of silicon, and the remainder being iron with the usual impurities; said spring being characterized by having the properties produced by treatment of such an alloy by maintaining the same at a temperature of substantially 1700 to 1800 degrees F. for substantially two hours, followed by slow cooling and a much shorter heating to approximately the same temperature with a subsequent slow cooling, and a cold working to its final size, whereby the spring has the property of remaining substantially stable in respect of its elasticity over the normal range of atmospheric temperatures from 0 to 150 degrees F.

5. A spring made of an alloy comprised of nickel substantially 35 percent, chromium substantially 5 percent, manganese substantially 5.5

- percent, tungsten substantially 2 percent, silicon substantially 0.5 percent, carbon in an amount not exceeding 0.75 percent, and the balance iron; said spring being characterized by having the properties produced by treatment which includes a heating in the range from 1700 1800 degrees F. for not more than two hours, a slow cooling, a preliminary cold drawing reduction, an annealing heating in the range from 1800 to 1900 degrees F. in a non-oxidizing atmosphere for approximately two minutes, and a final drawing degrees F;

HOWARD w. RUssEm 5 

